In catheter examinations of the heart, a number of angiographic x-ray images of the heart are usually generated from various directions, a contrast agent typically being injected during the recording. The angiograms of the vascular system that are thus obtained may be of assistance, for example, in locating the site of a lesion that is to be treated, or else they may be used as (static) road maps for navigating a catheter during a subsequent medical intervention.
Moreover, so-called intravascular ultrasound probes (IVUS probes) are used, which can be guided for example by means of a catheter through a vessel and generate ultrasound section images transversely to the vessel axis. Ultrasound images are often generated in a so-called pullback sequence using an IVUS probe. In this case, the IVUS probe is pulled back through the vessel at a defined speed while at the same time recording a series of ultrasound images. The IVUS images provide useful additional information about the vessel or a vessel lesion, for example the length of a vessel section affected by a disease, the minimum/maximum thickness of a vessel, the type of a deposit and the like. WO 2005/024729 discloses a device, used to display a vessel or a section of a vascular system, comprising the following components:    a) a (data) memory in which a sequence of intravascular ultrasound images is stored, the ultrasound images being indexed by the respective locations (x) of their recording in the vessel. Said ultrasound images may have been generated, for example, with the aid of an intravascular ultrasound probe. In particular, the images may come from an IVUS pullback sequence, wherein as the IVUS probe is being pulled back, the respective stopping location of the IVUS probe in the vessel is determined in parallel by means of further imaging. The latter may moreover be estimated from existing images of the vascular system (angiographs).    b) a data input for information which describes (at least) a current location in the vessel. By way of example, a pointer (mouse, etc.) could be connected to this input, by means of which pointer a user indicates, on a road map, a current location of interest to him in the vessel, or else a locating device could be connected to said input, which locating device detects, for example by means of magnetic fields, the current stopping location of an intervention device on a catheter.    c) a display unit, such as a monitor, for displaying images of the vessel.
The device disclosed in WO 2005/024729 comprising the described components is furthermore designed to select from said memory at least one ultrasound image and to display it on the display unit, wherein the ultrasound image corresponds to the current location in the vessel indicated at the data input. By way of example, an ultrasound image whose associated recording location is identical to the current location or is no more than a predefined distance from the latter may be selected from the memory. The selection function may be implemented in the device for example by means of a suitably programmed microprocessor.